Exploring The Relative Astringency of Tea Catechins and Distinct Astringent Sensation of Catechins and Flavonol Glycosides via an In Vitro Assay Composed of Artificial Oil Bodies

Abstract

Artificial oil bodies covered by a recombinant surface protein, caleosin fused with histatin 3 (a major human salivary peptide), were employed to explore the relative astringency of eight tea catechins. The results showed that gallate-type catechins were more astringent than non-gallate-type catechins, with an astringency order of epicatechin gallate > epigallocatechin gallate > gallocatechin gallate > catechin gallate > epigallocatechin > epicatechin > gallocatechin > catechin. As expected, the extension of brewing time led to an increase in catechin content in the tea infusion, thus elevating tea astringency. Detailed analysis showed that the enhanced proportion of gallate-type catechins was significantly higher than that of non-gallate-type catechins, indicating that tea astringency was elevated exponentially, rather than proportionally, when brewing time was extended. Rough surfaces were observed on artificial oil bodies when they were complexed with epigallocatechin gallate (a catechin), while a smooth surface was observed on those complexed with rutin (a flavonol glycoside) under an atomic force microscope and a scanning electron microscope. The results indicate that catechins and flavonol glycosides induce the sensation of rough (puckering) and smooth (velvety) astringency in tea, respectively.

Widely targeted metabolomic analysis reveals effects of yellowing process time on the flavor of vine tea (Ampelopsis grossedentata)

“…This indicated that flavanols normally exist in the form of gallic ester in the tea, and the hydrolysis of these substances under high temperature and high humidity conditions leads to the decrease of their content and the up-regulation of gallic acid (220.96–252.09%) and methyl gallic acid (234.83–280.33%) in the middle and late stage of yellowing. An in vitro assay described the astringency order as epicatechin gallate > epigallocatechin gallate > gallocatechin gallate > catechin gallate > epigallocatechin > epicatechin > gallocatechin > catechin, which testified the trans from gallate-type catechins to non-gallate-type catechins was beneficial to taste (C. T. Liu & Tzen, 2022 ). Gallic acid produced from the hydrolysis of flavanols has been associated with the enhanced umami taste and sweet of green tea infusion ( Kaneko, Kumazawa, Masuda, Henze, & Hofmann, 2006 ).…”

Extraction and Purification of Catechins from Tea Leaves: An Overview of Methods, Advantages, and Disadvantages

“…Catechins hold promise in materials science and nanotechnology; they are investigated for their role in developing bioactive coatings, films, and nanoparticles with applications in drug delivery, tissue engineering, and environmental remediation [125,126].…”

Artificial oil bodies: A review on composition, properties, biotechnological applications, and improvement methods

“…Meanwhile, the thickness of the emulsion is proportional to the astringency. Based on this, Liu and Tzen (2022) further investigated the astringency of the eight tea catechins utilizing AOBs, offering the possibility of their application in industry.…”